ASTM D6476-12(2017)e1
(Test Method)Standard Test Method for Determining Dynamic Air Permeability of Inflatable Restraint Fabrics
Standard Test Method for Determining Dynamic Air Permeability of Inflatable Restraint Fabrics
SIGNIFICANCE AND USE
5.1 For matters relating to lot acceptance of commercial shipments and conformity to specification or other standard, refer to Section 13 of this test method.
5.2 This test method is useful in the selection and design validation of permeable, uncoatable fabrics used in inflatable restraint cushions. The dynamic conditions and higher pressure differentials of this test method may better simulate the inflation and deflation cycle of an airbag module during deployment than do the steady-state conditions of Test Method D737.
5.2.1 Only uncoated, permeable fabrics should be used. Use of coated fabrics may yield invalid results and potentially damage the test apparatus.
5.3 Within the limits of variance expressed in Section 12, this test method is useful for design validation and may be suitable for incorporation in a material specification or for lot acceptance testing of commercial shipments. Caution is advised on very low permeability fabrics or with the 200 cm3 size test head because between-laboratory precision as presented in Section 12 may be as high as 21 %.
5.4 This test method may be used for materials other than inflatable restraint fabrics which experience dynamic air permeability in sudden bursts. In such cases, the physical apparatus or its software algorithms may require modification to provide suitability for use.
5.5 Due to the split-second time interval for testing, the pressure versus time data is subject to recording anomalies and electronic noise. The data should be digitally filtered to obtain the underlying smooth pressure curve prior to data analysis. The software in the apparatus includes a reliable algorithm both to smooth the curve and to determine the exponent of air permeability.
5.6 It is inherent in the design and operation of this equipment that major components key to the calibration and measurements are specific to the individual test head. The size or permeability measuring range of the test head is typically chosen to ...
SCOPE
1.1 This test method covers the procedures used to determine under dynamic airflow conditions the high pressure permeability of permeable, uncoated fabrics typically used for inflatable restraints. For the determination of air permeability of inflatable restraint fabrics under low pressure conditions at steady-state air flow, refer to Test Method D737.
1.2 Procedures and apparatus other than those stated in this test method may be used by agreement of purchaser and supplier with the specific deviations from the standard acknowledged in the report.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Buy Standard
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation:D6476 −12 (Reapproved 2017)
Standard Test Method for
Determining Dynamic Air Permeability of Inflatable Restraint
Fabrics
This standard is issued under the fixed designation D6476; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes were made to 4.1 in October 2018.
1. Scope D2904 Practice for Interlaboratory Testing of a Textile Test
Method that Produces Normally Distributed Data (With-
1.1 This test method covers the procedures used to deter-
drawn 2008)
mine under dynamic airflow conditions the high pressure
D6799 Terminology Relating to Inflatable Restraints
permeability of permeable, uncoated fabrics typically used for
E691 Practice for Conducting an Interlaboratory Study to
inflatable restraints. For the determination of air permeability
Determine the Precision of a Test Method
of inflatable restraint fabrics under low pressure conditions at
steady-state air flow, refer to Test Method D737.
3. Terminology
1.2 Procedures and apparatus other than those stated in this
3.1 For all terminology relating to D13.20, Inflatable
test method may be used by agreement of purchaser and
restraints, refer to Terminology D6799.
supplier with the specific deviations from the standard ac-
3.1.1 The following terms are relevant to this standard:
knowledged in the report.
average dynamic air permeability (ADAP), dynamic air per-
meability (DAP), cushion, exponent of dynamic air permeabil-
1.3 The values stated in SI units are to be regarded as
ity (EXP, ) inflatable restraint, inflator, module, standard
standard. No other units of measurement are included in this
atmosphere for testing textiles
standard.
3.2 For all other terms related to textiles, see Terminology
1.4 This standard does not purport to address all of the
D123.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
4.1 A volume of dessicated compressed air at known vol-
mine the applicability of regulatory limitations prior to use.
ume and pressure passes through a fabric specimen into the
1.5 This international standard was developed in accor-
standard atmosphere for testing textiles. During the portion of
dance with internationally recognized principles on standard-
the test cycle which simulates airbag inflation, the pressure
ization established in the Decision on Principles for the
differential pressure across the specimen rises to a value
Development of International Standards, Guides and Recom-
corresponding to a peak inflation pressure. During the portion
mendations issued by the World Trade Organization Technical
of the test cycle which simulates airbag deflation, the pressure
Barriers to Trade (TBT) Committee.
differential drops to 0 kPa as the air passes through the
2. Referenced Documents
specimen. The time to reach the maximum pressure and the
subsequent time for the pressure to decrease correspond to
2.1 ASTM Standards:
similar times in an airbag deployment.
D123 Terminology Relating to Textiles
D737 Test Method for Air Permeability of Textile Fabrics
4.2 Software algorithms integral to the apparatus smooth
D1776 Practice for Conditioning and Testing Textiles
out the pressure data and determine the values for ADAP and
EXP.
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
5. Significance and Use
and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.
5.1 For matters relating to lot acceptance of commercial
Current edition approved Feb. 1, 2017. Published March 2017. Originally
approved in 2000. Last previous edition approved in 2012 as D6476–12 (2017).
shipments and conformity to specification or other standard,
DOI: 10.1520/D6476-12R17E01.
refer to Section 13 of this test method.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D6476−12 (2017)
5.2 This test method is useful in the selection and design specimen in a range sufficient to meet the conditions of a
validation of permeable, uncoatable fabrics used in inflatable material specification for dynamic air permeability testing of
restraint cushions.The dynamic conditions and higher pressure inflatable restraint fabrics, with a tolerance of 6 2 %, mounted
differentials of this test method may better simulate the in a static or low pressure area in the test fixture that does not
inflation and deflation cycle of an airbag module during interfere with airflow.
deployment than do the steady-state conditions of Test Method
6.3 Air Compressor andAir Desiccating Cartridge, capable
D737.
of charging the pressure vessel in the test head to the specified
5.2.1 Only uncoated, permeable fabrics should be used. Use
pressure up to 400 kPa.
of coated fabrics may yield invalid results and potentially
6.4 Mounting Fixture, capable of retaining the fabric speci-
damage the test apparatus.
men over the test orifice without stretching the specimen and
5.3 Within the limits of variance expressed in Section 12,
without air leakage at the periphery of the test area.
this test method is useful for design validation and may be
6.5 ElectricalFiringPulseSource,suitableforactuatingthe
suitable for incorporation in a material specification or for lot
inflation and for communicating with the data acquisition
acceptance testing of commercial shipments. Caution is ad-
system dependent on an electrical signal.
visedonverylowpermeabilityfabricsorwiththe200cm size
test head because between-laboratory precision as presented in 6.6 Data Acquisition System, suitable for recording the
output of the pressure transducers versus elapsed time of
Section 12 may be as high as 21 %.
airflow.
5.4 This test method may be used for materials other than
6.7 Filter Requirements, data sampling rate, transducer
inflatable restraint fabrics which experience dynamic air per-
frequency response, and amplifier frequency response shall be
meability in sudden bursts. In such cases, the physical appa-
such that minimal effect on accuracy of the data occurs. The
ratus or its software algorithms may require modification to
accuracy of the pressure transducers, amplifiers, and timers
provide suitability for use.
within the test apparatus shall be calibrated to within 63%.
5.5 Due to the split-second time interval for testing, the
pressure versus time data is subject to recording anomalies and
7. Sampling
electronic noise. The data should be digitally filtered to obtain
7.1 Dynamic air permeability testing is a destructive test
the underlying smooth pressure curve prior to data analysis.
and therefore necessitates sampling procedures if used in
The software in the apparatus includes a reliable algorithm
conjunction with lot acceptance of commercial shipments.
both to smooth the curve and to determine the exponent of air
7.2 Lot Sample:
permeability.
7.2.1 For acceptance testing, the lot size is the quantity of
5.6 It is inherent in the design and operation of this
fabric finished in one production day or as agreed upon
equipment that major components key to the calibration and
between the purchaser and the supplier.
measurements are specific to the individual test head. The size
7.2.2 Unless otherwise agreed upon between the purchaser
or permeability measuring range of the test head is typically
and the supplier, take as a lot sample all the rolls in a
chosen to correspond to the fabric specimen to be tested. The
commercial shipment. Consider the rolls to be the primary
precision of this test method is highly dependent on the size of
sampling units.
the test head. The precision of the data collected using one test
7.3 Laboratory Sample
head should be used to estimate the precision of data collected
7.3.1 Anentirerolloffabricorafull-widthcutfromtheend
using a different test head, even on the same apparatus.
of a roll within a lot sample constitutes a laboratory sample.
5.7 Itismandatorythatfabricspecimensbeconditionedand
7.4 Test Specimens:
tested in standard atmosphere for testing textiles.
7.4.1 Test specimens are the pieces of fabric that actually
undergo testing. Cut or mark specimens from the end of each
6. Apparatus
roll of fabric in the laboratory sample, as indicated in the
6.1 Removable Test Head, containing a Pressure Vessel of
material specification or equivalent. Cut 165 by 330 mm
known volume capable of being charged pneumatically from 0
rectangular specimens from the full-width fabric sample, or
to no less than 400 kPa with a tolerance of 6 3.0 %, of
mark similarly sized areas across the full-width fabric sample
sufficient volume to challenge adequately the fabric being
without cutting individual specimens.
tested, equipped with a solenoid release valve mechanism, a
7.4.2 If areas of full width fabric are tested without cutting
test chamber, and a circular orifice with an area of 50 cm ; and
individual specimens, position test areas representing a broad
equippedwithameansofmeasuringandadjustingthepressure
distribution across the length and width, preferably along the
range in increments of 1 kPa, a minimum range between
diagonal of the laboratory sample, and no nearer the edge than
pressure set points of 5 kPa and rise and fall ranges in ms
one tenth its width.
(milliseconds) sufficient to meet the conditions of a material
specification for dynamic air permeability testing of inflatable
8. Conditioning
restraint fabrics.
8.1 Precondition test specimens in accordance with Practice
6.2 Pressure Transducers and Rigid Wall Pickup Tubes, D1776 or as agreed upon between the purchaser and the
suitable for measuring the pressure differential of the fabric supplier.
´1
D6476−12 (2017)
8.2 Prior to testing, bring the test specimens to moisture 11. Report
equilibrium at ambient atmospheric pressure, at 21 6 1°C, and
11.1 State that the tests were conducted in accordance with
at 65 6 2 % relative humidity, unless directed to do otherwise
this test method for determining the dynamic air permeability
by an agreement by the purchaser and supplier.
of inflatable restraints fabrics.
8.3 Equilibrium is considered to have been reached when 11.1.1 If deviation from this test method occurred, any
the increase in mass of the specimen in successive weighings reference to this test method shall state: “Testing was per-
made at intervals of not less than 2 h does not exceed 0.1 % of formed in accordance with ASTM D6476, with the following
the mass of the specimen. changes:”
11.2 The purchaser and supplier shall determine the exact
9. Procedure
form of the test report. Unless otherwise specified, report the
9.1 Select and condition specimens in accordance with 8.1.
following information:
9.2 Mount the fabric specimen on the test fixture, ensuring
11.2.1 Fabric designation,
that the retention mechanism clamps the fabric tightly with
11.2.2 Lot identification,
minimal tension and without damage or wrinkling. 11.2.3 Date of report,
11.2.4 Name of person certifying report,
9.3 Perform all system calibrations.
11.2.5 Relevant specification,
9.4 Enter the specimen number into recording portions of
11.2.6 Number of specimens used in each test,
the data acquisition.
11.2.7 Tests performed, and data obtained,
9.5 Ensurethepressurevesselispressurizedwithdesiccated 11.2.8 Laboratory conditions if other than standard, and
airtoapressuresufficientlyhightotestthespecimenwithinthe 11.2.9 Deviations from standard procedures and apparatus.
pressure ranges specified.
12. Precision and Bias
9.6 In accordance with the applicable material specification
or laboratory guideline, select and install the appropriate test 12.1 Bias—For multifilament fabrics such as those used for
inflatable restraints, there is no standard reference material
head for the fabric type to be measured.
availabletoserveasanacceptedstandardvaluefordynamicair
9.7 Preset the start, upper, and lower pressure limits.
permeability testing. In the absence of a known true value, the
9.7.1 Unless otherwise stated in the customer specification,
accuracy of this test method cannot be determined.
the test head size, and starting pressure should be selected such
12.2 The analysis of precision of test results using this test
that an average peak pressure of 100 6 10 kPa is reached
during the test. Also, unless otherwise stated in the customer method is meaningful both within-laboratory and between-
laboratory with multiple operators.
specification, the Lower Limit should be set to 30 kPa and the
Upper Limit should be set to 70 kPa.
12.3 An Interlaboratory Test was planned and conducted
on uncoated fabrics covering a range of permeabilities typi-
9.8 Establish data acquisition system response to pressure
inputs. cally used in inflatable restraint cushions in accordance with
Practice E691 and Practice D2904. For inflatable restraint
9.9 Initiate the starting sequence and note the response of
fabrics, the typical range of permeabilities is between zero and
the data acquisition system to verify successful airflow.
10 cfm when measured in accordance with Test Method D737.
9.10 Record maximum differential pressure in kPa, time to
Two variables,ADAPand EXPONENTwere studied.Analysis
maximum pressure in ms, or whatever data points are required
was done using SAS 6.1, PROC. GLM, and PROC.
by the material specification.
VARCOMP. Three components of variance - single-operator,
within-laboratory, and between-laboratory - were statistically
9.11 Remove the specimen from the test stand and mark it
calculated to determine precision of this test method.
as having been tested.
12.4 Precision of ADAP—For the components of variance
9.12 On the test report, record the data required by the
listed in Table 1, two averages of observed values should be
material specification.
considered significantly different at the 95 % probability level
NOTE 1—The unit of permeability commonly used forADAPmeasure-
if the difference equals or exceeds the critical differences listed
ment is mm/s. A velocity of 1 mm/s is the mathematical equivalent of a
3 2.
in Table 2
permeability of 0.1 cm /(cm s). Permeability and velocity are considered
interchangeabl
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D6476 − 12 (Reapproved 2017) D6476 − 12 (Reapproved 2017)
Standard Test Method for
Determining Dynamic Air Permeability of Inflatable Restraint
Fabrics
This standard is issued under the fixed designation D6476; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—Editorial changes were made to 4.1 in October 2018.
1. Scope
1.1 This test method covers the procedures used to determine under dynamic airflow conditions the high pressure permeability
of permeable, uncoated fabrics typically used for inflatable restraints. For the determination of air permeability of inflatable
restraint fabrics under low pressure conditions at steady-state air flow, refer to Test Method D737.
1.2 Procedures and apparatus other than those stated in this test method may be used by agreement of purchaser and supplier
with the specific deviations from the standard acknowledged in the report.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D123 Terminology Relating to Textiles
D737 Test Method for Air Permeability of Textile Fabrics
D1776 Practice for Conditioning and Testing Textiles
D2904 Practice for Interlaboratory Testing of a Textile Test Method that Produces Normally Distributed Data (Withdrawn 2008)
D6799 Terminology Relating to Inflatable Restraints
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 For all terminology relating to D13.20, Inflatable restraints, refer to Terminology D6799.
3.1.1 The following terms are relevant to this standard: average dynamic air permeability (ADAP), dynamic air permeability
(DAP), cushion, exponent of dynamic air permeability (EXP, ) inflatable restrain,restraint, inflator, module, standard atmosphere
for testing textiles
3.2 For all other terms related to textiles, see Terminology D123.
4. Summary of Test Method
4.1 A volume of dessicated compressed air at known volume and pressure passes through a fabric specimen into the standard
atmosphere for testing textiles. During the portion of the test cycle which simulates airbag inflation, the pressure differential
pressure across the specimen rises to a value corresponding to a peak inflation pressure. During the portion of the test cycle which
This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.
Current edition approved Feb. 1, 2017. Published March 2017. Originally approved in 2000. Last previous edition approved in 2012 as D6476–12. –12 (2017). DOI:
10.1520/D6476-12R17.10.1520/D6476-12R17E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
D6476 − 12 (2017)
simulates airbag deflation, the pressure differential drops to 0 kPa as the air passes through the specimen. The time to reach the
maximum pressure and the subsequent time to for the pressure to decrease correspond to similar times in an airbag deployment.
4.2 Software algorithms integral to the apparatus smooth out the pressure data and determine the values for ADAP and EXP.
5. Significance and Use
5.1 For matters relating to lot acceptance of commercial shipments and conformity to specification or other standard, refer to
Section 13 of this test method.
5.2 This test method is useful in the selection and design validation of permeable, uncoatable fabrics used in inflatable restraint
cushions. The dynamic conditions and higher pressure differentials of this test method may better simulate the inflation and
deflation cycle of an airbag module during deployment than do the steady-state conditions of Test Method D737.
5.2.1 Only uncoated, permeable fabrics should be used. Use of coated fabrics may yield invalid results and potentially damage
the test apparatus.
5.3 Within the limits of variance expressed in Section 12, this test method is useful for design validation and may be suitable
for incorporation in a material specification or for lot acceptance testing of commercial shipments. Caution is advised on very low
permeability fabrics or with the 200 cm . size test heathead because between-laboratory precision as presented in Section 12 may
be as high as 21 %.
5.4 This test method may be used for materials other than inflatable restraint fabrics which experience dynamic air permeability
in sudden bursts. In such cases, the physical apparatus or its software algorithms may require modification to provide suitability
for use.
5.5 Due to the split-second time interval for testing, the pressure versus time data is subject to recording anomalies and
electronic noise. The data should be digitally filtered to obtain the underlying smooth pressure curve prior to data analysis. The
software in the apparatus includes a reliable algorithm both to smooth the curve and to determine the exponent of air permeability.
5.6 It is inherent in the design and operation of this equipment that major components key to the calibration and measurements
are specific to the individual test head. The size or permeability measuring range of the test head is typically chosen to correspond
to the fabric specimen to be tested. The precision of this test method is highly dependent on the size of the test head. The precision
of the data collected using one test head should be used to estimate the precision of data collected using a different test head, even
on the same apparatus.
5.7 It is mandatory that fabric specimens be conditioned and tested in standard atmosphere for testing textiles.
6. Apparatus
6.1 Removable Test Head, containing a Pressure Vessel of known volume capable of being charged pneumatically from 0 to no
less than 400 kPa with a tolerance of 6 3.0 %, of sufficient volume to challenge adequately the fabric being tested, equipped with
a solenoid release valve mechanism, a test chamber, and a circular orifice with an area of 50 cm ; and equipped with a means of
measuring and adjusting the pressure range in increments of 1 kPa, a minimum range between pressure set points of 5 kPa and
rise and fall ranges in ms (milliseconds) sufficient to meet the conditions of a material specification for dynamic air permeability
testing of inflatable restraint fabrics.
6.2 Pressure Transducers and Rigid Wall Pickup Tubes, suitable for measuring the pressure differential of the fabric specimen
in a range sufficient to meet the conditions of a material specification for dynamic air permeability testing of inflatable restraint
fabrics, with a tolerance of 6 2 %, mounted in a static or low pressure area in the test fixture that does not interfere with airflow.
6.3 Air Compressor and Air Desiccating Cartridge, capable of charging the pressure vessel in the test head to the specified
pressure up to 400 kPa.
6.4 Mounting Fixture, capable of retaining the fabric specimen over the test orifice without stretching the specimen and without
air leakage at the periphery of the test area.
6.5 Electrical Firing Pulse Source, suitable for actuating the inflation and for communicating with the data acquisition system
dependent on an electrical signal.
6.6 Data Acquisition System, suitable for recording the output of the pressure transducers versus elapsed time of airflow.
6.7 Filter Requirements, data sampling rate, transducer frequency response, and amplifier frequency response shall be such that
minimal effect on accuracy of the data occurs. The accuracy of the pressure transducers, amplifiers, and timers within the test
apparatus shall be calibrated to within 6 3 %.
7. Sampling
7.1 Dynamic air permeability testing is a destructive test and therefore necessitates sampling procedures if used in conjunction
with lot acceptance of commercial shipments.
7.2 Lot Sample:
´1
D6476 − 12 (2017)
7.2.1 For acceptance testing, the lot size is the quantity of fabric finished in one production day or as agreed upon between the
purchaser and the supplier.
7.2.2 Unless otherwise agreed upon between the purchaser and the supplier, take as a lot sample all the rolls in a commercial
shipment. Consider the rolls to be the primary sampling units.
7.3 Laboratory Sample
7.3.1 An entire roll of fabric or a full-width cut from the end of a roll within a lot sample constitutes a laboratory sample.
7.4 Test Specimens:
7.4.1 Test specimens are the pieces of fabric that actually undergo testing. Cut or mark specimens from the end of each roll of
fabric in the laboratory sample, as indicated in the material specification or equivalent. Cut 165 by 330 mm rectangular specimens
from the full-width fabric sample, or mark similarly sized areas across the full-width fabric sample without cutting individual
specimens.
7.4.2 If areas of full width fabric are tested without cutting individual specimens, position test areas representing a broad
distribution across the length and width, preferably along the diagonal of the laboratory sample, and no nearer the edge than one
tenth its width.
8. Conditioning
8.1 Precondition test specimens in accordance with Practice D1776 or as agreed upon between the the purchaser and the
supplier.
8.2 Prior to testing, bring the test specimens to moisture equilibrium at ambient atmospheric pressure, at 21 6 1°C, and at 65
6 2 % relative humidity, unless directed to do otherwise by an agreement by the purchaser and supplier.
8.3 Equilibrium is considered to have been reached when the increase in mass of the specimen in successive weighings made
at intervals of not less than 2 h does not exceed 0.1 % of the mass of the specimen.
9. Procedure
9.1 Select and condition specimens in accordance with 8.1.
9.2 Mount the fabric specimen on the test fixture, ensuring that the retention mechanism clamps the fabric tightly with minimal
tension and without damage or wrinkling.
9.3 Perform all system calibrations.
9.4 Enter the specimen number into recording portions of the data acquisition.
9.5 Ensure the pressure vessel is pressurized with desiccated air to a pressure sufficiently high to test the specimen within the
pressure ranges specified.
9.6 In accordance with the applicable material specification or laboratory guideline, select and install the appropriate test head
for the fabric type to be measured.
9.7 Preset the start, upper, and lower pressure limits.
9.7.1 Unless otherwise stated in the customer specification, the test head size, and starting pressure should be selected such that
an average peak pressure of 100 6 10 kPa is reached during the test. Also, unless otherwise stated in the customer specification,
the Lower Limit should be set to 30 kPa and the Upper Limit should be set to 70 kPa.
9.8 Establish data acquisition system response to pressure inputs.
9.9 Initiate the starting sequence and note the response of the data acquisition system to verify successful airflow.
9.10 Record maximum differential pressure in kPa, time to maximum pressure in ms, or whatever data points are required by
the material specification.
9.11 Remove the specimen from the test stand and mark it as having been tested.
9.12 On the test report, record the data required by the material specification.
NOTE 1—The unit of permeability commonly used for ADAP measurement is mm/s. A velocity of 1 mm/s is the mathematical equivalent of a
3 2.
permeability of 0.1 cm /(cm s). Permeability and velocity are considered interchangeable terms.
10. Equipment Calibration
10.1 For inflatable restraints, all test equipment used in accordance with these test methods shall be certified for calibration
annually by an independent agency or equipment manufacturer whose results are traceable to the National Institute of Science and
Technology (NIST) or other national standards laboratory. The test parameters of the equipment shall be tested within the operating
ranges covered in the material specification or equivalent document.
´1
D6476 − 12 (2017)
11. Report
11.1 State that the tests were conducted in accordance with this test method for determining the dynamic air permeability of
inflatable restraints fabrics.
11.1.1 If deviation from this test method occurred, any reference to this test method shall state: “Testing was performed in
accordance with ASTM D6476, with the following changes:”
11.2 The purchaser and supplier shall determine the exact form of the test report. Unless otherwise specified, report the
following information:
11.2.1 Fabric designation,
11.2.2 Lot identification,
11.2.3 Date of report,
11.2.4 Name of person certifying report,
11.2.5 Relevant specification,
11.2.6 Number of specimens used in each test,
11.2.7 Tests performed, and data obtained,
11.2.8 Laboratory conditions if other than standard, and
11.2.9 Deviations from standard procedures and apparatus.
12. Precision and Bias
12.1 Bias—For multifilament fabrics such as those used for inflatable restraints, there is no standard reference material available
to serve as an accepted standard value for dynamic air permeability testing. In the absence of a known true value, the accuracy
of this test method cannot be determined.
12.2 The analysis of precision of test results using
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.